Thanks! This river came out of a tunnel from underneath the glacier on the side and then spilled over the bottom edge of it at the end. It must have picked up all the dirt while it was underneath.

You can see here what the glaciers on the south side of Cuerno look like. As far as I can tell, they are similar to the ones on Rainier. If you look closely, near the very bottom of the image you can make out this waterfall.